This document instructs you on how to set up a Java programming environment for your Mac OS X computer. It also provides a step-by-step guide for creatingand compiling a Java program in IntelliJ and executing itfrom the command line.

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You will need a Mac runningMac OS X 10.13 (High Sierra) to Mac OS X 10.15 (Catalina).

The installer installs and configures a Java programming environment, includingOpenJDK 11 andIntelliJ IDEA, Community Edition 2020.1.

• Log in to the user account in which you will be programming.Your account must have Administrator privileges.
• Download the Mac OS X installerlift-java.pkg.
• Double-click lift-java.pkg to install the software.Enter your Mac OS X password when prompted and use all of the default options.

  Warning

  If you have previously used IntelliJ,run this installer only if you want a clean re-install.The installer overwrites IntelliJ IDEA CE.app andany previous IntelliJ 2020.1 settings.

• Delete lift-java.pkg (if it is not automatically deleted).

You will develop your Java programs in an application called IntelliJ IDEA, Community Edition.

IntelliJ organizes Java programs into projects.In our context, each project corresponds to one programming assignment.A typical project contains Java programs, associated data files, andcourse-specific settings (such as compiler options, style rules, and textbook libraries).

• Download the project for your programming assignment to a convenient location(such as the Desktop).

  [ sample project for COS 126 (Princeton) ]

  [ sample project for COS 226 (Princeton) ]

  [ sample project for Computer Science: Programming with a Purpose (Coursera) ]

  [ sample project for Algorithms, Part I (Coursera) ]

  Double click the zip file to unzip.This creates a project folder with thename of the corresponding programming assignment (such as helloor percolation).Delete the zip file.

  
  

  Warning

  The project folders contain course-specific information. Be sure to downloadthe one corresponding to your institution and course.

  
  

• Launch IntelliJ via Finder → Applications → IntelliJ IDEA CE.app.
• When you launch IntelliJ for the first time,
  • IntelliJ may displaytheJetBrains privacy policy.Scroll down and Accept.
  • IntelliJ may ask if you want to send anonymous usage statistics to JetBrains. Choose your preferred option.
• To open a project from the Welcome screen,click Open and select the project folder.You should see an assignment logo (in the main editor window) and a list of project files (in the Project View sidebar at left).
  When you launch IntelliJ for the first time,it may take a minute or two to index your files;some features (such as auto importing) will be unavailable until this process completes.

  
  

  Warning

  Do not select Create New Project;this option is intended for advanced programmers.Also, always use Open with a project folder, not an individual file.
  
  
• When you are finished working, select the menu optionIntelliJ IDEA → Quit IntelliJ IDEA (⌘Q) to exit IntelliJ.The next time you launch IntelliJ, your recent projectswill appear in the Welcome screen for easy access.

Now you are ready to write your first Java program.IntelliJ features many specialized programming toolsincluding line numbering, syntax highlighting, bracket matching, auto indenting,auto formatting, auto importing, variable renaming, and continuous code inspection.

• To create a new Java program:
  • Re-open IntelliJ and the project (if you closed it in the previous step).
  • Click the project name in the Project View sidebar (at left), so that itbecomes highlighted.

    
    

  • Select the menu option LIFT → New Java Class.When prompted, type HelloWorld for the Name and click OK.

  
  

• In the main editor window, complete the Java programHelloWorld.java exactly as it appears below.(IntelliJ generates the gray boilerplate code automatically,along with the course header block comment.)If you omit even a semicolon, the program won’t work.
• As you type, IntelliJ highlights different syntactic elementsin different colors.When you type a left bracket, IntelliJ adds the matching right bracket.When you begin a new line, IntelliJ indents it.

  
  

• To save the file, select the menu option File → Save All (⌘S).When you save the file, IntelliJ re-formats it (if necessary).

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Now, it is time to execute (or run) your program.This is the exciting part, where your computer follows the instructionsspecified by your program.Before doing so, you must compile your program intoa form more amenable for execution on a computer.

• Select the program that you wish to compile and execute in the the Project View sidebar. The program should now appear in the main editor window.
• To compile your program,select the menu optionLIFT → Recompile 'HelloWorld.java' (⌘B).If the compilation succeeds, you will receive confirmationin the status bar (at bottom).

  If the compilation fails, a Recompile panel will open up (at bottom),highlighting the compile-time errors or warnings.Check your program carefully for typos, using the error messages as a guide.

• To execute your program,select the menu option LIFT → Run 'HelloWorld' with Arguments (⌘E).Since this program takes no command-line arguments, click OK.

  You should see the output of the program (in white), along with a messagethat the program finished normally (with exit code 0).

Tip

Use the LIFT menu to compile and execute your program from IntelliJ.The Build and Run menus support additional options for advanced programmers.

Also be sure that the main editor window is active before using the LIFTmenu (e.g., by clicking the code you want to compile or execute).

The command line is a simple and powerful mechanism forcontrolling your programs (e.g., command-line arguments,file redirection, and piping).IntelliJ supplies an embedded terminalfor easy access to the command line.

• Select the menu option View → Tool Windows → Terminal (⌘2).
• This will launch a Bash terminal where you type commands.You will see a command prompt that looks something like this:

  The ~/Desktop/hello is the current working directory, where~ is shorthand for your home directory.

• To compile your program,type the following javac command.More specifically, type the text in yellow that appears on the same line as thecommand prompt.Assuming that the file HelloWorld.java is in the current working directory,you should not see any compile-time errors or warnings.
• To execute your program,type the following java command:You should see the output of your program beneath the line on which you typed the command.

  
  

  Tip

  Typically, you should compile from IntelliJ(because IntelliJ highlights the lines on which anycompile-time errors or warnings occur) and execute from the command line(because the command line makes it is easy to specify command-line argumentsand use file redirection).

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To make our textbook libraries accessible to Java from the command line,you will use our wrapper scripts.

• Computer Science: An Interdisciplinary Approach (including COS 126 students).The programBarnsley.javauses our standard drawing and standard random libraries in stdlib.jar to draw aBarnsley fern.First download Barnsley.java.Then, use the Finder to move itto a project folder (such as hello).Finally, to compile and execute it,type the following commands in the terminal:When you execute the program, a standard drawing window will appearand an image like this one will be generated, one point at a time:

  To get your command prompt back, close the standard drawing window.

• Algorithms, 4th Edition (including COS 226 and Coursera students).The programCollidingDisks.javauses various libraries in algs4.jarto simulate the motion of n disks subject to the lawsof elastic collision.First download CollidingDisks.javaThen, use the Finder to move it to a project folder (such as percolation).Finally, to compile and execute it,type the following commands in the terminal:When you execute the program, a standard drawing window will appearwith an animation of 20 colliding disks.To get your command prompt back, close the standard drawing window.

  
  

  Frequently Asked Questions

  
  

  
  

  I installed IntelliJ and Java using the lift-java.pkg installerlast semester or year. Should I rerun this semester?

  Yes. This installer includes IntelliJ 2020.1and Java 11.The old installer may have used an earlier version of IntelliJ or Java.

  I previously used either the introcs.app or algs4.app installer.Should I use the lift-java.pkg installer?

  Yes. This installer includes IntelliJand Java 11 (instead of DrJava and Java 8).

  What happens if I rerun the lift-java.pkg installer?

  It will re-install and re-configure OpenJDK 11, IntelliJ,SpotBugs, PMD, Checkstyle, our textbook libraries,and wrapper scripts.

  The installer failed. How can I investigate why?

  Check the installer log at /var/log/lift.log.

  I have Mac OS X 10.12 (Sierra). Is that too old?

  Yes.Yes. IntelliJ 2020.1 requires Mac OS X 10.13 (or newer).

  How long will the installer take to complete installation?

  Once downloaded, it should take about a minute.If you have anti-malware protection software running (such as McAfee Endpoint), it couldtake 5–10 minutes.

  What does the lift-java.pkg installer do?

  In short, it installs and configures Java, IntelliJ,SpotBugs,PMD,Checkstyle,and our textbook libraries,along with accompanying command-line tools.Here is a more detailed list:

  • Installs OpenJDK 11.0.7.
  • InstallsIntelliJ 2020.1.1with customized user preferences,available indepedently as lift-intellij.pkg.
  • Installs the following command-line tools for Java, available independently aslift-cli.pkg.
    • The textbook librariesstdlib.jar andalgs4.jar.
    • Java wrapper scripts, includingjavac-algs4 and java-algs4.
    • Custom.bashrc,.bash_profile, and.inputrc files.As a precaution, the installer will do this only if detects no preexistingbash configuration files.
    • SpotBugs 4.0.3;our SpotBugs configuration file spotbugs.xml;and wrapper script spotbugs.
    • PMD 6.15.0;our PMD configuration file pmd.xml;and wrapper script pmd.
    • Checkstyle 8.31;various configuration files(checkstyle-cos126.xml,checkstyle-cos226.xml,checkstyle-coursera.xml, andcheckstyle-suppressions.xml);custom checks checkstyle-lift.jar;and wrapper script checkstyle.

  How is the software licensed?

  All of the included software is licensed under various open-source licenses.

  • IntelliJ IDEA, Community Edition is licensed under theApache License, Version 2.0.
  • OpenJDK 11 is licensed under theGNU General Public License,version 2, with the Classpath Exception.
  • SpotBugs is licensed under theGNU Lesser Public License, Version 2.1.
  • Checkstyle is licensed under theGNU Lesser Public License, Version 2.1.
  • PMD is licensed under a BSD-style license.
  • stdlib.jar and algs4.jar are licensed under theGNU General Public License, Version 3.

  What’s the sha256sum of lift-java.pkg?

  e5ef947039280e0b0520fd7bd3aff8a0373719b96b1745c08a42441f6554fafe

  Can I run the installer from the command line?

  Yes. Use the command sudo installer -verbose -pkg lift-java.pkg -target /

  How can I uninstall the software?

  • To uninstall OpenJDK 11,delete the following directory:
    • /Library/Java/JavaVirtualMachines/jdk-11.0.7.jdk/
  • To uninstall IntelliJ, delete the following:
    • /Applications/IntelliJ IDEA CE.app
    • ~/Library/Application Support/JetBrains/IdeaIC2020.1/
    • ~/Library/Caches/JetBrains/IdeaIC2020.1/
    • ~/Library/Logs/JetBrains/IdeaIC2020.1/
  • To uninstall SpotBugs, PMD, Checkstyle,and our textbook libraries, delete the following directory:
    • /usr/local/lift/
  • To uninstall our wrapper scripts, delete the following files:
    • /usr/local/bin/javac-{algs4,introcs}
    • /usr/local/bin/java-{algs4,introcs}
    • /usr/local/bin/jshell-{algs4,introcs}
    • /usr/local/bin/spotbugs
    • /usr/local/bin/pmd
    • /usr/local/bin/checkstyle

  Java FAQ

  Can I use a vendor and version of Java other than OpenJDK 11?

  Yes.You may use any version of Java 8, Java 9, Java 10, or Java 12, from either Oracle or OpenJDK.However, if you do so, you will need to manually configure the Platform SDK and Project SDK viaIntelliJ via File → Project Structure.

  How can I check which version of Java is installed (and where it is installed)?

  Type the following commands in the terminal:It’s important that the Java version numbers match and that you see the number11,but the rest is not critical.

  How does this custom version of IntelliJ different from the standard one?

  IntelliJis an industrial-strength integrated development environment (IDE),suitable for use by professional programmers.The installer configures your user preferences to make itmore suitable for use by novice programmers:

  • Disables all built-in plugins except Terminal and JUnit. Installs the SpotBugs, Checkstyle-IDEA, Run-with-Arguments, Save-Actions, and Archive browser plugins.
  • Eliminates or reduces various popup elements (lightbulbs, code folding, breadcrumbs, gutter markers, notifications, parameter hints).
  • Simplifies menus and toolbars, hiding advanced options.
  • Disables live templates and postfix completion.
  • Adopts the Obsidian Black color scheme.
  • Auto-configures Java upon installation.
  • Adds a few keyboard shortcuts.

  The course-specific project folders perform additional customizations:

  • Streamlines autocomplete to display only relevant libraries(such as java.lang,java.util, and algs4.jar).
  • Configures SpotBugs and Checkstyle with course-specific rules.
  • Provides course-specific libraries (such as algs4.jar).
  • Enables auto-formatting of code on save.
  • Enables auto-importing of Java libraries.

  How can I manually configure the Platform SDK and Project SDK in IntelliJ?

  The installer should configure the Platform SDK automatically.To configure it manually,

  • Navigate to File → Project Structure → Platform Settings → SDKs.
  • Click the + symbol (top left) to add an SDK.
  • Locate an SDK. A typical location for a Java SDK onMac OS X is /Library/Java/JavaVirtualMachines/adoptopenjdk-11.jdk/Contents/Home/.
  • Use the shorthand name suggested by IntelliJ(e.g., 11 for version 11.0.7).

  To manually configure the Project SDK,

  • Navigate to File → Project Structure → Project Settings → Project.
  • Choose the desired Project SDK from the drop-down list.
  • Be sure to use 8 as the Project language level, as our autogradercurrently supports only Java 8 features.

  What are the most important IntelliJ menu options to remember?

  Here are the most important ones (and their shortcuts).

  • LIFT → New Java Class (⌘N). Create a new Java class.
  • LIFT → Recompile (⌘B). Compile the current program.
  • LIFT → Run with Arguments (⌘E). Run the current program with command-line arguments.
  • LIFT → Open in Terminal (⌘T). Open a new Terminal tab.
  • File → Save All (⌘S). Save (and reformat) all open files.
  • View → Tool Windows → Project (⌘1). Show/hide the Project View sidebar.
  • View → Tool Windows → Terminal (⌘2). Show/hide the Terminal window.

  Any special characters to avoid when naming IntelliJ projects or files?

  Do not use an exclamation point (!) as the last characterin the project folder (or any directory name along the path to your project folder);that will confuse both IntelliJ and Checkstyle.

  How can I create a new project in IntelliJ?

  If you want to inherit all of the properties of an existing project,

  • Use the Finder to copy the project folder,giving it your preferred name.
  • Delete any unwanted files.
  • Be sure to keepthe .iml file (which defines the project),the .idea subdirectory (which containsthe IntelliJ course preferences), andthe .lift subdirectory (which contains the courselibraries).

  To create a new project from scratch, you can use the Create New Project option from theWelcome screen. But, we do not recommend this approach for novice programmers.

  Can I use a version of IntelliJ that is more recent than 2020.1.1?

  Yes, though if it is 2020.2 (or above),you will need to migrate your user preferences.

  How I can I restore the original IntelliJ settings(instead of the abbreviated novice-friendly ones)?

  • To restore the menus and toolbars: Preferences → Appearances & Behavior → Menus and Toolbars → Restore All Defaults.
  • To restore all settings: Help → Find Action → Restore Default Settings.

  Command-Line / Embedded Terminal FAQ

  When I compile or execute a program from the command line that uses one of thetextbook libraries, I get an error that it cannot find the library. How can I fix this?

  Make sure that you are using the appropriate wrapper script,such as javac-algs4or java-algs4.

  How should I configure Bash?

  If you followed our instructions, our wrapper scripts (such asjavac-algs4 andjava-algs4)should already be available.

  Our autoinstaller customizes the command line in a few ways by copying these three configuration files:.bashrc,.bash_profile, and.inputrc.Note that the autoinstaller will copy these files only if none of them already exists.If you had previous versions and wish to replace your versions with ours, type the following commands:

  How do I break out of a program in an infinite loop?

  Type Ctrl-C.

  How do I specify EOF to signal that standard input is empty?

  On Mac OS X and Linux, type EnterCtrl-D.On Windows, type EnterCtrl-ZEnter,even in Git Bash.

  How can I run SpotBugs, PMD, and Checkstyle from the command line?

  The installer includes wrapper scripts to simplify this process.

  • To run SpotBugs 4.0.3, type the following command in the terminal:The argument must be a list of .class files.Here is a list ofbug descriptions.
  • To run PMD 6.15.0, type the following command in the terminal:The argument must be either a single .java file ora directory containing one or more .java files.Here is a list of bug patterns.
  • To run Checkstyle 8.31, type one ofthe following commands in the terminal, depending on whether you are COS 126, COS 226, or Coursera student:The argument must be a list of .java files.Here is a list ofavailable checks.